Many high-power RF (radio frequency) and microwave applications include devices, such as switched power amplifiers, high-level mixers, TR (transmit receive) switches and series FET (field effect transistors) power amplifiers which require switching elements that are capable of handling high voltages and high currents (e.g., power amplifiers), switching at extremely high frequencies (e.g., microwave applications), and are isolated from surrounding structures & devices (e.g., the impedance increases).
As power and efficiency requirements increase, it becomes more difficult to switch devices in shorter times and still maintain isolation between devices and supplies. High power devices have more internal capacitance from terminal to terminal and also more external capacitance from terminals to ground. Eventually, for device circuits, switching elements such as those shown in FIGS. 1A-C, become unrealizable and ineffective.
Presently, there are various circuits (e.g., class D, E, F and S power amplifiers, GaAs ring mixers, optical data links) that have high efficiency and are fast switching. However, these circuits only operate at very low-power levels, such as low IP3 (third-order intercept point), so these current solutions are not helpful for larger power or microwave applications.
Presently, solutions to maximize switching times have been developed using multi-stage devices, such as Darlingtons pairs (e.g., piggy back transistor configuration), cascode FETs, series FETs, and MMICs (Monolithic Microwave Integrated Circuits), however isolation in the biasing schemes and input drive schemes limit performance.
Spatial combining of devices have been developed. Spatial combining of devices provides limited isolation between devices, associated losses and limited bandwidth.
Therefore, it may be desirable to provide a switching element that may operate with high voltage and currents, switches quickly, provides an isolated RF input and power supply and is also isolated from surrounding structures and devices.